Silicones (i.e., organosiloxanes) are polymers containing alternating silicon and oxygen atoms in the backbone with various organic groups attached to the silicon atoms. Silalkylenesiloxane copolymers include alkylene backbone units without unsaturation and also include monovalent hydrocarbon groups attached to silicone atoms. Both silicones and silalkylenesiloxanes are useful materials for a wide variety of applications (e.g., rubbers, adhesives, sealing agents, release coatings, antifoam agents). Because of their biocompatibility, silicones present a low risk of unfavorable biological reactions and have therefore gained the medical industry's recognition. Such materials are useful in a wide variety of medical devices. There are, however, limited materials available for medical device applications. In addition, there is a need for improved silicone materials that can be used in the medical industry, particularly those with good strength and tear resistance.
Prior to the present invention, silalkylenesiloxane copolymers have been prepared by three methods. Ring opening polymerization of cyclic silethylenesiloxane is disclosed in U.S. Pat. No. 5,117,025 (Takago et al.). Condensation polymerization of silanol terminated silalkylene oligomers is disclosed in U.S. Pat. No. 5,386,049 (Kishita et al.). Step growth hydrosilylation polymerization between a hydride terminated organosiloxane and an unsaturated aliphatic hydrocarbon that contains 2 carbon-carbon double bonds or one carbon-carbon double bond and one carbon-carbon triple bond is disclosed in U.S. Pat. No. 5,442,083 (Kobayashi).
U.S. Pat. No. 5,442,083 (Kobayashi) states that the ring opening polymerization of cyclic silethylenesiloxane is not advantagous for producing silalkylenesiloxane copolymers. As reported in Andrianov et al., Inst. Of Heteroorganic Cpds., p. 661, translated from lzvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 739-44 (1971), a partial depolymerization occurs in this method, which therefore leads to reduced yields of the silalkylenesiloxane copolymer.
Step growth condensation polymerization of silanol terminated fluids yields copolymers that have silanol end groups. To make the copolymer end-functional, for example, vinyidimethylsilyl terminated, another synthetic step is required. This is a disadvantage. In addition, degrees of polymerization (Dp) from step growth silanol condensation polymerizations of disilanolsilalkylene compounds have been reported to be no greater than 180. See, U.S. Pat. No. 5,386,049 (Kishita et al.) and Benouargha et al., Eur. Polym. J., 33, p. 1117 (1997). This is a disadvantage.
Hydrosilylation step growth polymerization as a method of silalkylenesiloxane copolymer synthesis also contains inherent disadvantages. In order to produce high Dp copolymer, the stoichiometry of the silylhydride and unsaturated hydrocarbon moieties must be as close to 1:1 as possible. Side reactions which disturb this balance limit the Dp of said copolymer by creating terminating groups on unsaturated hydrocarbon monomers. For example, it is known in the art that transition metal catalysts typically used for hydrosilylation reactions can cause the isomerization of a terminal carbon-carbon double bond to an internal position. See, Harrod et al., Organic Synthesis via Metal Carbonyls, 2, John Wiley & Sons, New York, p. 673 (1977), Cundy et al., Adv. Organometallic Chem., 2, p. 253 (1973), and Speier, Adv. Organometallic Chem., 17, p. 407 (1979). This is a disadvantage. This isomerization renders the monomers less suceptible to hydrosilylation.
Silalkylenesiloxane copolymers having a Dp as high as 10,000 are disclosed in U.S. Pat. No. 5,484,868 (Kobayashi). However, step growth hydrosilylation polymerization was the method used to produce the copolymers and no examples were provided which would circumvent the disadvantages outlined above.
The following lists of documents disclose information regarding siloxane compounds.
TABLE 1a ______________________________________ Patents U.S. Pat. No. Inventor(s) Issue Date ______________________________________ 5,117,025 Takago et al. 05/26/92 5,239,034 Takago et al. 08/24/93 5,241,034 Herzig et al. 08/31/93 5,386,007 Herzig et al. 01/31/95 5,386,049 Kishita et al. 01/31/95 5,442,083 Kobayashi 08/15/95 5,484,868 Kobayashi 01/16/96 5,516,832 Kennan et al. 05/14/96 5,525,696 Herzig et al. 06/11/96 5,531,929 Kobayashi 07/02/96 5,581,008 Kobayashi 12/03/96 5,696,211 Chung et al. 12/09/97 5,703,190 Dauth et al. 12/30/97 ______________________________________
TABLE 1b ______________________________________ Non-U.S. Patents Patent No. Country Publication Date ______________________________________ EP 0 709 403 A1 EPO 05/01/96 W0 96/20964 PCT 07/11/96 W0 96/35732 PCT 11/14/96 ______________________________________
TABLE 1c ______________________________________ Nonpatent Documents ______________________________________ Andrianov et al., "Polymerization of 2,2,6,6-Tetramethyl-1-oxa-2,6- disilacyclohexane, "Inst. of Heteroorganic Cpds., p. 661, Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 739- 44 (1971) Benouargha et al., "Hybrid Silalkylene Polysiloxanes: Synthesis and Thermal Properties", Eur. Polym. J., 33, pp. 1117-1124 (1997). Cundy et al., "Organometallic Complexes with Silicon-Transition Metal or Silicon-Carbon-Transition Metal Bonds", Advances in Organometallic Chemistry, Academic Press, New York (1973), pp. 253-311. Dvornic et al., "Polymerization by Hydrosilation. 2. Preparation and Characterization of High Molecular Weight Poly[(1,1,3,3- tetramethyldisiloxanyl)ethylene] from 1,3-Dihydridotetramethyldisiloxane and 1,3-Divinyltetramethyldisiloxane", Macromolecules, 27, pp. 7575- 7580 (1994). Harrod et al., "Hydrosilation Catalyzed by Group VII Complexes", Organic Synthesies via Metal Carbonyls, John Wiley & Sons, New York (1977), pp. 673-705. Marciniec et al., Comprehensive Handbook on Hydrosilylation, Pergamon Press, Ltd; Tarrytown, New York; 1992; pp. 35-38. Odian, Principles of Polymerization, John Wiley & Sons, New York (1981), pages 82-87. Speier, "Homogeneous Catalysis of Hydrosilation by Transition Metals", Advances in Organometallic Chemistry, Academic Press, New York (1979), pp. 407-447. ______________________________________
All patents, patent applications, and publications listed above are incorporated by reference in their respective entireties. As those of ordinary skill in the art will appreciate readily upon reading the application, certain of the information disclosed in the above-listed documents may be utilized in the monomers, polymers, their preparation methods, and the devices disclosed and claimed herein.